Grinding machine



March 12, 1935. Y' c. HERFURTH y 1,993,840

GRINDING MACHINE Filed Feb. 29, 1952 2 sheets-sheet 1- llllllmlllllh.

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' GRINDING MACHINE Filed Feb. 29, 1952 2 Sheets-Sheet 2 v d U l' 3mm/vbo@ CHARLES HERFURTH Patented Mar. `L2,v 1935 PATENT vOFFICE 1,993,840 l GRINDINGk MACHINE Charles Herfurth, Cincinnati, Ohio, assigner to Cincinnatiy Grinders Incorporated, Cincinnati,

Ohio, a corporation of Ohio Application Februaryu29, 1932, Serial No. 595,709

4 Claims. l

lThisinvention relates to improvements in machine tools and especially to improvementsr in grindingmachines.

LAs is well known, a grinding machine operates most eiiiciently whenr its operative surface is traveling at'a definite speed, for eXample'six thousand peripheral feet afminute. Therefore,

a cylindrical or disk typegrinding wheel is rotated at a speed for causing the wheels surface toy travel at this speed and most machines are designed to rotate the maximum size wheel atthis speed whenl they are new. Frequently no means are providedwforv increasing'the 'speedof 'the wheel 'after it becomes reduced in diameter due to Wear or trimming or truing away so that the wheel-s surface. instead*l of traveling at lthe' recognized efficient rate `of speedv is actually traveling at aslower rate `of speed, causing the same to wear away at a rapid rate and increasing the cost of the products being ground thereby. It is,` therefore, one of the principal objects of' the present invention to provide means for autoe matically increasing the` speed of the Wheel as it is worn down.

Another object of the invention is the provision of simple means for effecting this increase of speed. I

.A further object of the' invention is the pro' visionv of a self-contained grinding wheelunit for 3 use with grinding machines and including its individual prime mover or motor that is automatically Vspeeded up as the wheel is Worn beyond a-definitepoint.

Other objects and advantages of the present invention should be readily apparent by reference to the following specifioationconsidered in conjunction With the accompanying drawingsfonning'a part thereof andit is to b'e understoodthat any modic'ations may be made in the exact struotural details 'there shown and ldescribedv within the scope 'of theappended claimswithout departing Vfrom `or exceeding the spirit of the invention.'

In the drawings:

' Figure 1 is an elevationalv'iew 'of a grinding machine' embodying the 'improvementsof' this invention.l v

AFigure 2 is Va top plan viewrof thefmachine K shown'in Figure 1'.

Figure 3' is -an elevational 'ew as seen from linea- 3 onFigure 2.1 f

- Figurefiis a sectional 'view'taken on line 4-4 ofFigure3. l

VFigure 5` is a sectional Tview taken Aon line 5 a 5'-'5 of AFigure-ZLvv v Figure 6 aA sectional viewtaken online' 6-60fFigure3. f f

` Figure 7 'is a diagrammatic View illustrating the electricalcircuit involved in this invention.

Figure 8 is a diagrammatic .View illustratingV a 5 modification of the' invention. y

Throughout the several views ofthe drawings simi-lar reference characters are employed tov denote the same or similar parts.

A machine embodying this invention may com- 10 prise a bed 10 having formed on the upper surface thereof guideways "for guiding a translatable table 11 duringits movement relative to the bed 10. Mounted on the table arecthe usual head stock`12 and tail stock'18 respectively support- 10 ing centers Maand 15 between which'the Work is mounted for movement withlthe table. Any desirable means may be providedfor effecting the translation of the tablefor example, the hand wheelm16l whichis operatively connected 'therewithV in the 'usual or desirable manner.vk

vThe bed has secured thereto and projecting from the-rear thereof' an' extension: 17 disposed transversely to the direction in which the work table 11 travels and has formedthereon ways' 25' 18 and '19 for the grinding' wheel carriage A20 movable relatively to the extension 17 toward andl from the work supporting table. The car-` riage 20has j ournaled therein a spindle'21 to one end of which is secureda grinding wheel 22 for rotation therewith. A motor 23 being' provided and having extendingtherefroma shaft 24 to which is secured a pulley or sheave 25 in alignment with a similar pulley or sheave 26 secured to the spindle 21. .Afben or other flexible trans- 35 mission means such as the V-slraped belts 27 being provided for connecting the pulleys 25 and 26 and for transmitting motion from the shaft 24 to the spindle 21.

/ yThelmotor 23 is adapted to be rotated at a speed for rotating thel spindle 21 at the necessary speed to aotuate' the operative face 28 of the grinding Wheel, whenv the wheel is the maximum size usablev in the machine, at the eiiicient'speed of approximatelysix thousand peripheral feet a minute. f This speed is' the recommended speed of wheel manufacturers today and it may be increased orldecreased depending on the particular type of wheel being used. The soie requirement as far as this application is concerned being that the peripheral speed of the surface 28 be at `the recognized most efiicientspeed.

As is Well known, a generous supply of Ycoolant must be supplied to the grinding 'wheel and work at vthe point Where they engage one an# other during grinding to prevent burning or otherwise damaging the surface of the work being produced. For this purpose, there is provided a pipe or conduit 29 connected at 30 to the usual pressure supply and terminating at 31 in a nozzle for directing the coolant stream to the desired point. The pipe 29 is supported by a bracket 32 having a pivotal. connection at 33 with a bracket 34 for adjusting the pipe toward and from the grinding wheel. The bracket 34 carrying the bracket 32 is adjustably mounted on the rod 35 for movement in a direction transversely of the axis of the grinding wheel. The rod 35 is keyed or otherwise securely mounted in a. bracket 36 integral with or secured to a guard 37 that substantially encloses the grinding wheel 22. In order to confine the coolant and insure its proper supply at the point of grinding, the guard 37 closely encircles the wheel 22 and must at all times be positioned in close proximity therewith. Therefore, as the wheel is worn away the guard is shifted toward the rear of the wheel as respects its grinding point in a radial direction relative thereto.

The guard 37 has secured to it in any desirable manner, such as by rivets 38, a bar or guide 39. 'This bar being provided intermediate its ends with a slot 40-through which a clamp bolt 41 passes for securing same to the carriage 20. The guard is supported by means of anti-friction rollers 42 and 43 each carried by a pad 44 formed on the side of the carriage adjacent the guard by means of pins 45 extending therethrough into the said pad 44. The under surface 45 of the bar 39 rests on the said rollers and rides therealong, as the vguard is shifted radially of the wheel.

It is well known that the speed of certain motors is increased by inserting resistance in series with the eld circuit, which is especially true of a direct current shunt wound motor. Therefore, if the resistance is shunted the speed of the motor is reduced and may be considered the normal speed thereof. As shown in Figure 7, the main electric lines or leads 47 and 48 have wired between them the prime mover or motor 23, the eld of which includes the conduits 49 and 50 having between them the field coil 51 and a resistance 52 between the conduit 50 and motor 23. By reference to this'gure, it will be noted that the conduit is shunted around a `resistance 53 and has electrically connected therein a switch 54 held normally in a closed position by means of a spring 55. From the foregoing it will be noted that if the switch 54 is opened the circuit through the conduit 50 will be broken and must pass through the resistance 53 thereby increasing the speed of the motor 23. Any suitable or desirable means may be provided for opening this switch 54, which should take place at a definite point in thewear of the grinding wheel or when its diameter is reduced ,to 'such a point that the speed thereof decreases the peripheral speed of the operative 5 face of the wheel beyond the efficient grinding point. As shown in the drawings, the guardV bar 39 is provided on its extreme rear end with a cam block 56 having formed thereon the cam face 57 for engagement with a roller 58 carried on the end of an arm 59. This arm 59 is pivoted at 60 which extends through a plate 6l secured to the side of the carriage 20. Secured to the plate 61 and projecting interiorly of the carriage 20 is a switch mechanism 62 carrying the usual or desirable parts for operating the switch 54 to break the electrical circuit. As shown in Figure 7, this mechanism may comprise a cam 63 on the end of the pivot stud 60 and operable therewith for opening the switch against the resistance of the spring 55.

'I'he operation of the device is as follows. A full size Wheel, shown in full lines in Figure 3, is mounted `on the grinding wheel spindle 21. The guard 37 is adjusted to the position, again shown in full lines in Figure 3, at which time the parts are in proper relation for confining the coolant spray to the machine and insuring the prope-r quantity of coolant being delivered to the point of contact between the wheel and Work where the actual grinding takes place. As the wheel is worn and trimmed away during practice the operative face 28 recedes necessitating the adjustment of the guard 37 radially of the wheel and toward the left, as seen in Figure 3. The surface 28 of the wheel eventually reaches the dot and dash line 64 of VFigure' 3, which represents substantially the size ofr the wheel when half worn away. As the guard 37 is adjusted radially of the wheel during this wearing away, asabove described, the cam block 56 is gradually approaching the roller 58 and when the wheel reaches its mid useful position the guard and parts carried thereby are in the position shown inv dotted lines inFigure 3, therebyactuating the arm 59 and opening the switch 54, cutting in to the electrical circuit the resistance 53 and speeding upv the rotation of the motor 23.- The new speed of the motor issuch that the peripheral face of the grinding wheel, as represented by the broken line 64, will be increased an amount to bring its peripheral travel up to the speed of the operative surface 28 so that the grinding wheel will effect the desired stock removal at the recognized efiicient rate.

The modification shown inl Figure 8 illustrates a plurality of resistance's 53a, 53h and 53e between the motor field 51a, and the motor. Each of these resistances is shunted by a conduit 50a, 50b and 50c so that the motor 23 is rotated at its normal speed as when a new full sized wheel is being used as' above described. However, in'- stead of stepping up the motor speed once during the life of thewheel it may be stepped up a plurality of times such as after each inch' of wear of the wheel. For this reason each of the shunt lines or leads 50a, 50h and 50c are provided with a switch such as 54 and indicated by the reference numerals 54a, 54h and 54c'respectively held cled by springs 55a, 55h and 55e. These switches are adapted vto be opened by cams 63a, 63h and 63e each being similar to the cam 63 andv each being carried by an arm similar to the arm 59. Therefore, instead of a single switch being carried by the carriage 20 a plurality of them is mounted thereon and each is successively actuated during the rearward adjustment of the guard 37` and .thereby at all times keeping the surface of the grinding' wheel traveling at its proper efficient speed.

What is claimed is:

' 1. In agrinding machine of the class described the combination of a bed, a grinding wheel carria'ge carried thereby, a spindle journaled in the carriage, a grinding wheel secured to the spindle, a primemover operatively connected with the spindle for rotating same and the grinding wheel secured thereto, said spindle and wheel being rotated at a rate to cause the operative faceof the wheel to have a peripheralA speed forl effecting 'etticient stock removal from a workpiecasid wheel being reduced in diameter due to wear and truing theerof and thereby reducing the peripheral travel of the wheel to a point below its efficient stock removal point, and means for increasing the rate of rotation of theA prime mover and rate of rotation of the spindle and grinding wheel for increasing the peripheral speed of the worn wheel to the point of initial peripheral travel, said means including an electrical resistance adapted to be inserted in the electrical circuit of the motor, a switch for connecting the resistance in the circuit, a guard enclosing the wheel `and adjustable relative thereto as the wheel is vworn away, a bar secured to the guard, means associated withA the bar for securing the guard to the carriage in adjusted positions relative to the wheel, and a cam mounted on the bar for closing the switch when the guard reaches a definite position in its range of adjustment representative of a wornor reduced wheel. y

2. In a grinding machine of the class described the combination of a bed, a grinding wheel carriage carried thereby, a spindle journaled in the carriage, a grinding wheelsecured to the spindle, a prime mover operatively connected with the spindle for rotating same and the grinding wheel secured thereto, said spindle and wheel being rotated at a rate to cause the operative face of the wheel to have a peripheral speed for effecting efficient stock removal from a work piece, said wheel being reduced in diameter due to wear and truing thereof and thereby reducing the peripheral travel of the wheel to a point below its efficient stock removal point, and means for increasing the rate of rotation of the prime mover andrate of rotation of the spindle and grinding wheel for increasing the peripheral speed of the worn wheel to the point of initial peripheral travel, said means including an electrical resistance adapted to be inserted in the electrical circuit of the motor, a switch for connecting the resistance in the circuit, a guard enclosing the Wheel and adjustable relative thereto as the wheel is worn away, a bar secured to the guard, means associated with the bar for securing the guard to the carriage in adjusted positions relative to the wheel, a cam mounted on the bar for closing the switch when the guard reaches a definite position in its range of adjustment representative of a worn or reduced wheel, and anti-friction means for permitting ready adjustment of the guard.

3. In a grinding machine ofthe class described the combination of a bed, a grinding wheel carriage mounted thereon for transverse movement relative thereto, a grinding wheel spindle journaled in the carriage, a grinding wheel secured to the spindle, a prime mover belted to the spindle for effecting its rotation and the grinding wheel secured thereto, said motor effecting the rotation of the grinding wheel, when full size, at. its most eflicient peripheral speed, the peripheral speed of the Wheel being reduced as the wheel is worn and trued away, a guard mounted onthe carriage for adjustment relative thereto to closely engage the wheel to confine the coolant usual with grinding wheels, and means carried by the carriagefor movement therewith and operable upon movement of the guard for increasing the peripheral speed of the worn and reduced wheel to its initialperipheral speed, said means including a resistance in the prime mover circuit, a switch on the carriage normally shunting the resistance, a bar on the guard for movement therewith as it is adjusted relative to the carriage and wheel, and cam means on said bar for actuating the switch.

4. In a grinding machine of the class described the combination of a bed, a grinding wheel carriage mounted thereon for transverse movement relative thereto, a grinding wheel spindle journaled in the carriage, a grinding Wheel secured to the spindle, a prime mover belted to the spindle for effecting its rotation and the grinding wheel secured thereto, said motor effecting the rotation of the grinding wheel, when full size, at its most efficient peripheral speed, the peripheral speed of the wheel being reduced as the wheel is worn and trued away, a guard mounted on the carriage for adjustment relative thereto to closely engage the Wheel to confine the coolant usual with grinding wheels, and means carried by the carriage for movement therewith and operable upon movement of the guard for increasing the peripheral speed of the worn and reduced wheel to its initial peripheral speed, said means including a resistance in the prime mover circuit, a switch on the carriage normally shunting the resistance, a bar on the guard for movement therewith as it is adjusted relative to the carriage and wheel, cam means on said bar for actuating the switch, and anti-friction means supporting the guard on the carriage to permit ready adjustment of the guard.

CHARLES HERFURTH. 

